bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/net/rxrpc/skbuff.c b/net/rxrpc/skbuff.c
new file mode 100644
index 000000000..e2169d1a1
--- /dev/null
+++ b/net/rxrpc/skbuff.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Socket buffer accounting
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/net.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/af_rxrpc.h>
+#include "ar-internal.h"
+
+#define select_skb_count(skb) (&rxrpc_n_rx_skbs)
+
+/*
+ * Note the allocation or reception of a socket buffer.
+ */
+void rxrpc_new_skb(struct sk_buff *skb, enum rxrpc_skb_trace why)
+{
+	int n = atomic_inc_return(select_skb_count(skb));
+	trace_rxrpc_skb(skb, refcount_read(&skb->users), n, why);
+}
+
+/*
+ * Note the re-emergence of a socket buffer from a queue or buffer.
+ */
+void rxrpc_see_skb(struct sk_buff *skb, enum rxrpc_skb_trace why)
+{
+	if (skb) {
+		int n = atomic_read(select_skb_count(skb));
+		trace_rxrpc_skb(skb, refcount_read(&skb->users), n, why);
+	}
+}
+
+/*
+ * Note the addition of a ref on a socket buffer.
+ */
+void rxrpc_get_skb(struct sk_buff *skb, enum rxrpc_skb_trace why)
+{
+	int n = atomic_inc_return(select_skb_count(skb));
+	trace_rxrpc_skb(skb, refcount_read(&skb->users), n, why);
+	skb_get(skb);
+}
+
+/*
+ * Note the destruction of a socket buffer.
+ */
+void rxrpc_free_skb(struct sk_buff *skb, enum rxrpc_skb_trace why)
+{
+	if (skb) {
+		int n = atomic_dec_return(select_skb_count(skb));
+		trace_rxrpc_skb(skb, refcount_read(&skb->users), n, why);
+		consume_skb(skb);
+	}
+}
+
+/*
+ * Clear a queue of socket buffers.
+ */
+void rxrpc_purge_queue(struct sk_buff_head *list)
+{
+	struct sk_buff *skb;
+
+	while ((skb = skb_dequeue((list))) != NULL) {
+		int n = atomic_dec_return(select_skb_count(skb));
+		trace_rxrpc_skb(skb, refcount_read(&skb->users), n,
+				rxrpc_skb_put_purge);
+		consume_skb(skb);
+	}
+}